The MSCP - part of Pima County's Sonoran Desert Conservation Plan - makes a streamlined ESA process possible thru a commitment to protect, manage, monitor and report on important habitats, landscapes and species in order to mitigate/offset impacts in other areas.

Some details from the MSCP FAQs (retrieved 4/25/2019):

As new development occurs some species listed in the Endangered Species Act will be impacted. Such impacts, whether they occur intentionally or unintentionally, may be illegal unless the U.S. Fish and Wildlife Service (Service) approves a plan to mitigate for these impacts. This approval requires the Service to issue a ‘Section 10 permit’, so called for its reference to the section of the Endangered Species Act.

Since 1999, Pima County and Pima County Flood Control District has been acquiring open space or flood prone lands through voter-approved bond programs. Many of these lands will be used to fulfill mitigation land requirements of the Section 10 permit. ... The amount of open space land the County currently has, along with some of the flood prone land owned by the District, appears to be sufficient to provide mitigation for at least the first 20 years of the Section 10 permit.

The page above is part of an example trip report to Pima County's Old Hayhook Ranch property in the Altar Valley at the base of the Coyote Mountains. The MSCP reports have been an interesting way for me to learn about some of Pima County's land acquisitions that may have never otherwise known about - from Pima County's Coyote Mountains Sites Acquisition Page:

Old Hayhook Ranch, located at the base of the Coyote Mountains in Altar Valley, is comprised of a number of old homestead claims and associated ranchlands located adjacent to the Coyote Wilderness Area and the Tohono O’odham Nation. Several parcels of the Old Hayhook Ranch were purchased by Pima County in 2005 from a private landowner for its outstanding natural and cultural resources.

In addition to its cultural values, it was determined to have high habitat value for more than 20 vulnerable species and the land includes a portion of a complex of Hohokam villages considered to be ancestral sites to the Tohono O’odham. The 839 acres parcel was consequently designated a high priority conservation area for acquisition to preserve these values. Historic Preservation bonds and a Recovery Land Acquisition Grant from the US Fish and Wildlife Service funded the acquisition.

Source: 2016 MSCP Annual Report Pdf available from Multi-species Conservation Plan - Pima County.